The introduction of catheters into blood vessels for a variety of purposes such as coronary angiography has been known for many years. Several techniques for introducing these catheters are available. One such technique is the cut-down method. Another is the Seldinger technique. This technique involves surgically opening a vein or artery with a needle, inserting a guidewire into the vein or artery through the lumen of the needle, withdrawing the needle, inserting over the guidewire a dilator located inside an associated sheath with a hemostasis valve, removing the dilator and inserting a catheter through the sheath and into the blood vessel.
Various types of hemostasis valves have been known in the prior art. However, in most cases, each hemostasis valve is designed for use with a specific size of catheter. Because adequate sealing around the catheter walls cannot be obtained for a variety of catheters having varying diameters using conventional hemostasis valves, it has not been possible to employ a single hemostasis valve with catheters of widely varying diameters.
These problems are particularly acute when the guidewire technique is used. Guidewires are of extremely small diameter, often as small as 0.025 inch (0.064 cm.). However, many catheters are relatively larger in diameter, for example, as large as about 0.120 inch (0.30 cm.) in diameter. Therefore, in the prior art it has been difficult to design a single hemostasis valve which will seal around both relatively large diameter catheters as well as relatively small diameter guidewires.
One method of solving this problem is shown in U.S. Pat. No. 5,092,857 which discloses a universal hemostasis cannula with hemostasis valve contained within a longitudinally extended valve housing, having a first opening and a central longitudinal passage communicating with an opposite second opening. This one-piece hemostasis valve comprises a receiving area, a sealing neck and a sealing chamber having opposite sealing exit lips with a support shoulder on the outside of said seal adjacent to the sealing neck to provide support for the seal. The support shoulder reduces the insertion and withdrawal force necessary for inserting dilators and guidewires of varying sizes through the cannula while still providing good "feel" for the medical practitioner when utilizing these products.
Another method of solving this particular problem is shown in U.S. Pat. No. 4,909,798 which discloses a universal hemostasis cannula with a hemostasis valve similar in design to that shown in U.S. Pat. No. 5,092,857 but without support shoulders. This valve has also solved some of the problems relating to sealing around extremely small diameter of guidewires with the relatively larger diameter of catheters, catheter introducers and dilators.
Another universal hemostasis valve is disclosed in U.S. Pat. No. 5,114,408. This device utilizes a one-piece seal located within a valve housing wherein the seal contains a sealing neck having a relatively small opening which communicates with a slit contained in a concave exit base of the seal. This valve has also been successful in solving some of the problems relating sealing around the extremely small diameter of guidewires used with the relatively larger diameter of catheters, catheter introducers and dilators.
Another method of solving this problem is disclosed in EP A2 0 344 907. This European patent application discloses a self-sealing catheter and guidewire introducer with a self-sealing gasket adapted to create a seal when a catheter or guidewire extends through the gasket. The sealing means disclosed by this application contains an outer half thickness and an inner half thickness which vary to permit the gasket to seal both smaller diameter guidewires and larger diameter catheters. A similar device is shown in U.S. Pat. No. 5,304,156.
Another hemostasis valve designed for use with a guidewire and catheter is disclosed in U.S. Pat. No. 4,946,133. This valve contains a cylindrical base having a central opening and a hollow convex dome-shaped member projecting from the base wherein the dome-shaped member has a slit formed in its external surface which extends inwardly to form a central self-sealing passage aligned with the central bore of the cylindrical base member. A similar device is shown in U.S. Pat. No. 5,106,054.
Another catheter introducer valve assembly is disclosed in U.S. Pat. No. 4,960,412 which discloses a first and second valve for preventing the flow of blood both when a catheter is inserted through the valve and when there is no catheter present. Similar devices are shown in U.S. Pat. Nos. 5,269,764, 5,211,634, 5,456,284 and 4,932,633.
Other devices designed to solve the problem of various sizes of catheters introduced as part of a surgical procedure have been disclosed, for example, in U.S. Pat. No. 4,000,739 which employs two gaskets to seal against the back pressure of blood in the cannula unit. The first, donut-shaped, gasket is provided with a hole slightly smaller than the diameter of the catheter to be inserted, while the second gasket is provided with a Y-shaped slit. However, when guidewires or catheters which are too small in diameter are inserted into this hemostasis valve, the sealing advantages of the first, donut-shaped gasket are no longer available because the larger diameter donut hole will not seal around the smaller diameter guidewire or catheter. Moreover, when catheters are employed having diameters which are extremely large in relation to the diameter of the hole in the donut-shaped gasket, the gasket may become separated from the hemostasis valve body or it may be unduly stretched so that it will not seal properly when a smaller sized catheter is inserted at a later time.
Hemostasis valves having similar problems to those discussed in U.S. Pat. No. 4,000,739 are disclosed in U.S. Pat. Nos. 4,673,393 and 4,610,665.
U.S. Pat. No. 4,436,519 discloses a seal containing a combination of a donut-shaped gasket and a cup-shaped gasket. As in other prior art seals where two gaskets are utilized to form the seal, the device described in the '519 patent suffers the same deficiencies because its donut-shaped gasket can only accept catheters having a limited range of diameter sizes. Moreover, this device is particularly susceptible to leakage when only a guidewire is in place.
U.S. Pat. No. 4,341,239 discloses a combination check-over-pressure relief valve similar in design to the '519 device containing a cylindrical main body portion which is supported by a radially outwardly extending flange and ribs as a stiffening means, wherein the ribs project from the surface of the main body portion.
U.S. Pat. No. 4,655,752 discloses a surgical cannula which does not employ donut-shaped gaskets. However, this cannula, like the other prior art cannulas, suffers from a lack of universality and from poor sealing. While two seals are employed, the second seal may only be used with catheters having a limited range of diameters and will provide little or no sealing for a guidewire.
German Patent No. 3,042,229 sets forth a hemostasis valve which may be used with catheters having a variety of diameters. However, it is extremely difficult to use this valve when relatively large diameter catheters are employed because the second seal is required to expand against the sidewalls of the cannula, thereby significantly increasing friction during insertion and the risk of hemodynamic dampening. Moreover, the sealing means of the device described in the '229 patent is formed from two separate pieces thereby increasing the difficulties of manufacture and the likelihood that one of the seals may become dislodged particularly during use with large sized catheters. A similar device is shown in U.S. Pat. No. 4,809,679.
Another problem shown by many prior art hemostasis cannulas is that the cardiologist must be able to "feel" the catheter as it is inserted through the gaskets or other sealing members of the hemostasis valve and ultimately into a blood vessel. If insertion of the catheter through the hemostasis valve is too difficult, the cannula unit may be rejected by cardiologists as being difficult to use during catheter insertion. Concomitantly, the use of hemostasis valves which exert undue pressure on the side walls of inserted catheters may lead to excessive hemodynamic dampening of the catheter. In other words, excessive pressure on the exterior side-walls of a catheter may cause a narrowing of the catheter's diameter, thereby altering measurement parameters within the catheter.
In addition, hemostasis valves have also experienced problems from collapse of a portion or portions of the valve during the withdrawal of the dilator and the insertion of the catheter. Further, repeated insertion and withdrawal of catheters and catheter related devices through conventional hemostasis valves has become more and more difficult. This increase in force which is necessary for insertion and withdrawal further reduces the usability of conventional hemostasis valves.
Accordingly, it is one aspect of this invention to prepare a hemostasis valve unit.
Another aspect of this invention is to prepare a hemostasis valve which permits the easy insertion and withdrawal of both guidewires and catheters.
Another aspect of the invention is to prepare a hemostasis valve which has sufficient strength not to collapse on repeated insertions and withdrawals of catheters.
Another aspect of this invention is to prepare a hemostasis valve which is universal in nature and may be used with a wide variety of both large and small diameter guidewires and catheters, without leakage.
It is another aspect of this invention to prepare a hemostasis valve which will not leak when a guidewire is inserted into a vein or artery through the valve.
Another aspect of this invention is to prepare a hemostasis valve which is universal in nature and which does not exert undue pressure on the side walls of an inserted catheter while still providing support for the valve in use.
It is a further aspect of this invention to prepare a hemostasis valve having a unitary sealing member forming at least two separate sealing sections.
It is yet another aspect of this invention to construct a hemostasis cannula unit which will permit the use of catheters having a wide variety of diameters, while at the same time allowing insertion of any of these catheters without undue pressure/friction thereby providing good surgical "feel" for all diameters of catheters.
These and other aspects are obtained by constructing the hemostasis cannula units of the present invention.